TPS55340: Assistance needed determining inductor value and confirming design values.

Hi Borislau,

I read through your post but can't find the schematic. I don't know the meaning of V3 so please share the schematic first.

Hi, my apologies, I forgot to add the following that it was reference design.
USB Power Supply Using TPS61088 to Support Quick Charge 2.0 Design Guide

I hope that clarifies things up.

From Page 1 of that document, in the block diagram, the following are changed:

* Boost Converter TPS61088 -> TPS55340 (TPS55340PWP)

* eFuse TPS2592AA -> TPS25910

From Page 14:

U3: V3 to BP changes to V3 to U1 FB next to V1 & V2.

I hope that makes more sense now.

The CHY100 supports the Class B 5V, 9V, 12V & 20V

Also, in reference to this section:
"Setting Output Voltage, I use the following formula as per datasheet: 1.229*(316/20.66+1)= 20.02V

• The 20.66 was derived from: 100k//95k3//127k//49k9."
  
  

I was referning to the datasheet for the TPS55340, p.10/11, p18.

Thank you.

Hi Borislau,

I'm afraid TPS55340 could support this case. 

TPS55340 is a boost converter so it cannot output 5V from a 2S Li-Po battery. And to generate 20V 3A output power, the average input current will be 20V*3A/6V/0.85=11.8A, exceeding the switch current limit of TPS55340.

LM5176 buck-boost controller could be used for this case.

Hi,

Sorry, I needed to clarify more on this line:

“since it does not have an ILIM (TPS55340), would using the ILIM from the TPS25910 be ok? (I’ll be using 66.5 kΩ for 3A limit)”

This was meant when operating at 5V DC and then can taper off, i.e: 5V 3A, 9V1.667A, 12V 1.25A, 20V 750mA etc, which is why I was asking the following:

“Can you please advise what the A values will be for 5V, 9V, 12V & 20V.”

I would have preferred the ILIM, since then there would still be for wattage at least up to the 12V mark and then could taper down, but would not have been much of an issue if it were 2S1P Li-Po/Li-Ion as compared to a 1S2P

I have had a look at the LM5176, but it will add slightly complexity to the pcb than needed at this stage as it will need four MOSFETs or 2 dual MOSFETs, plus extra cost, although it could be re-worked in to a later design.

I can re-do the design to use the batteries in parallel if it would make the design easier, since I was considering using the BQ25886 for charging, but can use a 1S charging IC, like one of the following:
BQ25896, BQ25606 or the bq24160A for the same charging power input from a 5V source. The charging circuit I can redo, as it is still very early stages for that section.

The sections have the following:

The eFuse and Charger interface have been finalised at this stage, but the boost or buck/boost hasn’t, and the charger is dependent on the power section (labelled Boost Converter).

I hope this makes more sense now.

Hi Borislau,

The main reason I don't recommend you using TPS55340 is this is a boost converter, only supporting Vout> Vin cases. So if using 2S1P Li-Po/ Li-Ion, you can't get 5V. I understand changing to LM5176 would increase total area and size.

TPS55340 would not support output 5V 3A, 9V1.667A, 12V 1.25A, 20V 750mA from 3.0-4.2Vin cases because the it fixed current limit minimum spec is 5.25A. Assuming 85% efficiency, average input current is 15W/0.85/3.0V=5.88A. 

TPS61178 is better for your case. Its input voltage range is 2.7V to 20V and output voltage range is 4.5V to 20V. Its current limit is 6.4A(min), big enough. 

There is no problem to use TPS25910. For CHY100,  you could use 316k as higher feedback resistor, 100k, 95.3k, 127k, 49.9k as lower feedback resistor.

Hi Zack,

Thank you for the reply.
What value inductor and any recommendations, would you have for an input voltage of 3V - 4.2V then for the TPS61178, and what A outputs would I be looking at for the previous values?

Thank you.

Boris

Edit: Would the solution on p.28 work with the differing FB resistors?

Hi Boris,

2.2uH inductor with Isat> 7A will meet the requirement.

'and what A outputs would I be looking at for the previous values?' Here what does A mean?

Vref=1.198V, Vout=Vref*(Rup/Rbottom+1). Vup=316k ohm, to get 5V, 9V, 12V, 20V output voltage, use 100k, 95.3k, 127k, 49.9k as bottom feedback resistors will get these four Vout separately.

Hi Zack,

Thanks for providing hte value.

The "A", is in referefence to the Amp output at each voltage stage, what can I expect at each output stage?

Thank you.

Boris

Edit: Just want to confirm that the following part will be acceptable: SPM6530T-2R2M TDK 8.4A